The present invention relates to a motor-driven chop saw having a lower blade guard arrangement, and more particularly to a lower blade guard arrangement in the chop saw, which is pivotally mounted for movement between a raised rest position and a lowered operational position.
A conventional chop saw generally provides an upper safety guard which partially encases a circular saw blade, and a swingable lower blade guard which covers the exposed portion of the saw blade when the saw is in the raised rest position. When the upper safety guard is pivotally moved to the lowered operational position about a pivot shaft, the swingable lower blade guard is rotated to expose the saw blade portion so as to chop a wooden or metal workpiece mounted on a saw table with the circular saw blade.
During the chopping, the exposed area of the saw blade must be as small as possible for the purpose of safety. Thus, the lower blade guard must sufficiently cover the exposed portion even during the chopping. For this, commonly U.S. Pat. No. 4,774,866 discloses a lower blade guard provided rotatably about a rotation axis of the circular saw blade, and a link mechanism for pivotally moving the lower blade guard in response to cut infeed motion of the circular saw blade so that the exposed area of the saw blade is minimized even during a chopping operation.
However, according to the conventional lower blade guard arrangement disclosed in the U.S. Patent, an optimum pivotally moving or displacing distance may not be obtainable in response to the pivotal motion of the circular saw blade due to the structure of the link mechanism. Further, it would be difficult in the conventional arrangement to control an amount of movement of the lower blade guard in accordance with various cutting position of the circular saw blade. For example, the lower blade guard may abut the workpiece even if the circular saw blade per se can still perform chopping (even if the circular saw blade can still further be pivotally moved downwardly). Due to the interference of the lower blade guard with the workpiece, further chopping work cannot be performed. Alternatively, due to inappropriate relationship between the swinging displacement of the circular saw blade and the pivotal displacement of the lower blade guard, the area of the exposed blade portion becomes temporarily large during chopping work, which incurs increased danger to an operator.